When completing an especially large bowel movement, one or more of the resulting turds breaches or "crowns" above the water. Not to be confused with the Massive Brown Crown or Gorgo the Beast Master, when one or more turds are so large that they extend above the toilet seat, requiring the pooper to stand up in order to break off the turd and finish.

Guy 1: "Dude, you were in the shitter forever! What were you doing, scuba diving?"
Guy 2: "Nah man, I just finished my Brown Crown. That thing was wonderful. I took a picture with my phone. I cried a little when I had to flush it."
Guy 1: "Well break out the picture, man!"

While in the bathroom ...
Friend 1: "Oh my god! I think I'm crapping out my soul!"
Friend 2 (at the next stall): "Bullshit! Let's compare dumps; I'll bet mine's bigger."
Both friends finish without wiping to compare dumps.
Friend 2: "Holy hell, man! You had a Brown Crown! That turd's almost touching the lid!"
Friend 1: "I know, man. That was almost a Massive Brown Crown. I almost want to name it!"